Holder for a crystalline rod in apparatus for crucible-free zone melting



United States Patent Inventor Carl-Heinz Vogel [56] References Cited "Wield, Germany UNITED STATES PATENTS QY A- g ifi 1,585,490 5/1926 Hainsworth 269/97X 1,257,022 5/1932 Hingley 287/111 Patented Dec. 15, 1970 Assignee Siemens Aktiengesellschaft 2659954 1 1/1953 woolsey' 24/279 Berlin and Munich Germany 2,174,459 9/1939 Borsetti 287/14 a corporation of Germany Primary ExaminerRobert C. Riordon Assistant Examiner-Donald D. Evenson At!0rneysCurt M. Avery, Arthur E. Wilfond, Herbert L.

Lerner and Daniel J. Tick ABSTRACT: In apparatus for crucible-free zone melting a substantially vertically extending end-supported crystalline rod, such as a semiconductor rod, connectable in substantially coaxial alignment with a shaft, there is an end holder for inter- HOLDER FOR A CRYSTALLINE ROD 1N APPARATUS FOR CRUClBLE-FREE ZONE g T g Fi 8 connecting the rod and the shaft, the end holder comprising 8 g guide means for receiving respective ends of the rod and the US. Cl 269/97, shaft, a plurality of clamping jaws pivotally mounted above 287/ l4, 287/1 1 1 one another at respective ends thereof on the guide means and Int. Cl B2 3k 37/04 having respective free ends, the clamping jaws being pivotable Field of Search ..24/ 132(LS), about respective axes parallel to the axis of the rod in a direction toward the rod axis, and means for yieldably connecting the free ends of the clamping jaws to the guide means.

263(SB). 263.3, 279; 269/97, 98, 32(N); Z79/44z285/l84, l85:287/lll,ll8, 12,14

HOLDER FOR A CRYSTALLINE ROD IN APPARATUS FOR CRUCIBLE-FREE ZONE MELTING My invention relates to holder for a crystalline rod, particularly a semiconductor rod, in apparatus for carrying out a crucible-free zone melting process.

In a crucible-free zone melting process, especially of a semiconductive materials, a melting zone produced preferably by an induction heating coil is passed through a rod shaped member of the material being processed. Thereby, impurities at one end of the rod are transported through the rod and are partly vaporized in a vacuum within which the process is generally carried out. The process is also often employed for growing monocrystals by fusing a monocrystalline seed crystal to one end of the rod and passing a melting zone repeatedly through the rod in a direction away form the seed crystal. The rod shaped member is generally clamped at both ends thereof in respective holders and is disposed substantially in a vertical position. The holders, in turn, are frequently secured on rotatable drive shafts which are also rectilinearly displaceable in the direction of the rode axis.

With the known holders of the aforementioned type, the connection between the drive shaft and the holder is effected by means of a clamping jaw slidable oradjustable against the drive shaft. For holding the crystalline rod, three pivotable levers are respectively mounted in two planes substantially perpendicular to the rod axis on a carrier member coaxially surrounding the rod. As disclosed in US. Pat. No. 3,191,924, the levers can be forced against the rod by means of screws and thereby clampingly surround it, very much like a chuck.

It is an object of my invention to provide a rod holder of the aforedescribed type which affords a secure clamping seat for the crystalline rod and the shaft yet requires relatively little cost of construction.

Another object of my invention is to provide such a holder which requires relatively little head room.

It is a further object of my invention to provide a holder of the foregoing type which will maintain a firm clamping connection undiminished between holder and shaft as well as between holder and crystalline rod even for conditions wherein the rod ends, the holder and the shaft are nonuniformly heated, for example, when the shaft is cooled by external means.

With the foregoing and other objects in view I provide in accordance with my invention a holder for a crystalline rod, especially a semiconductor rod, in apparatus for crucible-free zone melting wherein the rod, is held in a substantially vertical position and is connectable in coaxialy alignment at an end thereof with a holder shaft by means of a plurality of clamping jaws pivotable about respective axes parallel to the rod axis in a direction toward the rod axis. A common guide member is provided for receiving a respective end of the crystalline rod and the holder shaft. The clamping jaws are located above one another and are pivotable about respective ends thereof. Each of the clamping jaws has a free end which is yieldably or resiliently connected with the guidemember. The operation of the clamping jaws mounted on the common guide member is relatively simple, particularly since only one of the clamping jaws is generally sufficient for providing an adequate clamping seat for the rod end and the holder shaft.

In accordance with a further feature of my invention, the yieldably or resilient connection between the free ends of the clamping jaws respectively and the guide member comprises respective fastener means, preferably threaded bolts for fastening the clamping jaws to the guide member, and heat-re sistant plate springs disposed between the respective clamping jaws and the fastening means.

In accordance with other features of myinvention, the plate springs are distinguished by the fact that they exert a relatively large spring force and that the dimension thereof in a direction radial to the rod axis is virtually insignificant.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in holder for a crystalline rod, particularly a semiconductor rod, in a device for crucible-free zone melting, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalence of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. 1 is front elevational view of the holder constructed in accordance with my invention;

FIG. 2 is a top plan view of the holder in FIG. 1 in the open or outwardly swung position of the clamping jaws;

FIG. 3 is a side elevational view of the holder as viewed from the left hand side of FIG. 1;

FIG. 4 is a front elevational view of another embodiment of FIG. 1 having a holder for transversely adjusting a seed crystal; and v FIG. 5 is a side elevational view of FIG. 4.

Referring now to the drawings and first particularly to FIGS. 1 to 3 thereof, there is shown a holder 1 for a crystalline rod 2 and a holder shaft 3. The holder 1 is formed of a common guide member 4 as well as an upper clamping jaw 5 and a lower clamping jaw 6. The crystalline rod 2 can preferably be a monocrystalline seed crystal which is employed for monocrystal growing or pulling. The guide member 4 is provided with cutouts or recesses 7 and 8 in which the crystalline rod 2 and the holder shaft 3 are guided (FIG. 3). The recess 7 for the crystalline rod 2 is advantageously formed so that the rod 2 extends only along a small portion of the holder 1 in linear contact with the guide member 4. With this aim in view, the portion of the recess 7, for example, which lies opposite the upper and lower edges 5a and 5b of the upper clamping jaw 5, has the shape of an isosceles triangle (FIG. 2). The recess 8 for the preferably cooled holder shaft 3 is advantageously provided with a semicircular shape. The upper clamping jaw 5 is formed as a bellcrank, mounted laterally on the guide member 4 and pivotable at one end thereof about a pivot pin 9. The upper clamping jaw 5 advantageously has a C- shaped profile (FIG. 3), both transverse arms or the edges 5a and 5b of this C-shaped profile being directed during operative condition of the holder against the crystalline rod 2. Heat transfer from the highly heated crystalline rod 2 to the holder 1 is thereby impeded. The free end 10 of the upper clamping jaw 5 is provided with a slot 11 through which a fastening screw 12 is passed. In operative condition of the holder, the fastening screw 12 is inserted in a threaded bore formed in the guide member 4 (FIG. 3) and connects the upper clamping jaw 5 with the guide member 4. One or more heat-resistant compression springs, preferably plate springs 13, are disposed advantageously between the clamping jaw 5 and the fastening screw 12, and yieldably biases the clamping jaw 5 away from the head of the screw 12 against the guide member 4. The lower clamping jaw 6 is secured on a pivot pin 14 which is mounted in two projections 15 extending from the guide member 4. The holder shaft 3 is guided in respective semicircular recesses 8 and 16, formed respectively in the guide member 4 and in the lower clamping jaw 6 and mutually registerable to provide a substantially cylindrical clamping surface. An elastic clamping connection is produced between the lower clamping jaw 6 and the guide member 4 by means of a bolt or screw 17 mounted at the freely movable end 19 of the clampingjaw 6 as well as with compression springs, preferably plate springs 18, which act in a manner similar to the plate springs 13 for biasing the lower clamping jaw 6 yieldably against the guide member 4 in a direction away from the head of the screw 17.

It is, of course, self-evident that more than one clamping jaw 5, 6 respectively, can be employed for holding the crystalline rod 2 and connecting it to the holder shaft 3. A suitable heatresistant alloy of chromium-molybdenum-vanadium steel, in a composition such as is generally known to the man in the art, is suitable as material for the heat-resistant plate springs 13, 18. The clamping connection between the clamping jaws and 6 respectively and the guide member 4 can also be produced by any conventional fast-release connection such as a latching device located at the free end surfaces of the jaws and the substantially coplanar end surface of the guide member as shown in the plane of the drawings illustrated in FIG. 3, wherein the holder is illustrated in operative condition.

The aforedescribed holder can be modified so that it can be used also as a holder for transversely adjusting a seed crystal. A suitably modified embodiment is accordingly shown in H08. 4 and 5. The guide member 4 has a bipartite construction in the embodiment of FIGS. 4 and 5, the upper clamping jaw 5 being pivoted on the upper portion 4a of the guide member 4, and the lower clamping jaw 6 being correspondingly pivoted on the lower portion 4b of the clamping jaw 4. The mutual guidance of the separate divided guiding member 4a, 4b and the orientation of the seed crystal transversely to the axis of the rod 3 is effected by providing a guide bolt 19 carried by the guide member portion 4a and extending through an arcuate elongated slot guide 20 formed in the other guide member portion 4b and having a radius of curvature corresponding substantially to the length of the seed crystal. The guide bolt 19 is suitably threaded in a bore formed in the guide member portion 4a so as to bind the guide member portions 4 a and 4b together in the desired orientation.

lclaim:

1. ln apparatus for performing a crucible-free zone melting process on a substantially vertically extending end-supported crystalline rod, such as a semiconductor rod, connectable in substantially coaxial alignment with a shaft, the rod being heatable in the process to a temperature differing from that of the shaft, an end holder for interconnecting the rod and the shaft and being, in the process, at a temperature differing from that of the rod and the shaft, said end holder comprising guide means for'receiving respective ends of the rod and the shaft, a plurality of clamping jaws pivotally mounted above one another at respective ends thereof on said guide means and having respective free ends, said clamping jaws being pivotable about respective axes parallel to the axis of the rod in a direction toward the rod axis, and means for yieldably connecting said free ends of said clamping jaws to said guide means, so as to apply uniform clamping force at all times to the rod and the shafl, respectively, notwithstanding differences in the temperature of the rod, the shaft and said end holder,- said yieldable connecting means comprising a fastening member respectively extending between said clamping jaws and said guide means and heat-resistant compression springs disposed between the respective clamping jaw and fastening member, wherein said guide means comprises a first and a second separate portion on each of which one of said clamping jaws is pivotally mounted, and means for adjustably connecting said first and second portions to one another, said connecting means comprising a screw extending through an arcuate slot formed in one of said portions and threaded in a bore formed in the other of said portions. 

